54 ABSORPTION BY AQUEOUS VAPOUR. PART i. 



tion of the needle of the goniometer showed that the 

 absorptive power of the aqueous vapour exceeded that 

 of the dry air 80 times. Now since in the atmo- 

 sphere there is one molecule of aqueous vapour with an 

 absorptive power of 80 for every 200 atoms of oxygen 

 and nitrogen whose absorptive power is 1 like that of one 

 of its constituent atoms, it follows by comparison that 

 the absorptive power of the molecule is 16,000 times 

 greater than that of an atom of either oxygen 

 or nitrogen. From this enormous opacity to obscure 

 heat e it is certain that more than ten per cent, of the 

 terrestrial radiation from the soil of England is stopped 

 within ten feet of the surface of the soil ; remove for a 

 single summer night the aqueous vapour from the air 

 which overspreads the country, and you would assuredly 

 destroy every plant capable of being destroyed by a 

 freezing temperature.' 



The quantity of vapour in each place varies with the 

 latitude, the season, and other circumstances ; but when- 

 ever the amount of heat radiated from the earth sur- 

 passes the absorption, the remainder passes through 

 the vapour into space, and for the same reason the 

 residue of that coming from the sun passes through the 

 vapour and comes to the earth, so that whatever may 

 be the local differences it has been decidedly proved 

 with regard to the whole globe, that the quantity of 

 heat annually received from the sun is annually 

 radiated into space; the latter is a force lost to the 

 earth, nevertheless it does not interfere with the law 

 of the conservation of force which extends to the 

 universe. 



By observations made during ten scientific ascents in 

 a balloon to very great altitudes, Mr. Glaisher has 

 proved, that the theory of the uniform decrease of 

 temperature with, increase of elevation is no longer 

 tenable. Since the absorptive force of aqueous vapour 



